IN THE GARDEN THE RIGHT TREE FOR YOUR AREA.

Byline: JOSHUA SISKIN

Two recent e-mails raise several general questions on the subject of tree selection and care in the Valley:

Q: We live in Porter Ranch, and up until six months ago had a spectacularly large coral tree in our front yard. It showcased our property, and we enjoyed its shade and beauty for many years, having planted it 18 years ago. It tolerated the occasional cold spell and was healthy until recently. Now that the coral tree is gone, our front yard seems drab nd bare. We would like to replace it with Ficus Roxburghii, a tree we saw rowing in Santa Barbara. While it will not be as large as a coral tree, we love its enormous leaves and think it would be the perfect tree. Could you tell us what you know about this tree and also name a nursery where we might locate one?

- Bob and Ruth Heiser, Porter Ranch

A: Like the coral tree (Erythrina caffra), Ficus Roxburghii (also known as Ficus auriculata) is a semi-tropical tree that would be at risk in the colder parts of the Valley. Porter Ranch, however, since it is located in the hills on the Valley's northern edge, does not suffer the same cold experienced in places like Woodland Hills, Van Nuys and San Fernando. Cold air, just like rain, rolls down a hilly terrain, not remaining long enough to cause marginally cold-sensitive plants to freeze. Then again, the kind of severe freeze we experience every decade of so would be risky for these trees. As a general rule, it is wise to plant the largest tree you can find (and afford) where cold-sensitive species are concerned. The larger the specimen, the better chance it has of surviving that occasional deep freeze.

Coral trees are among the most charismatic trees on account of their big bicep limbs, flesh-colored bark, distinctive heart-shaped leaves and brilliant orange-red flowers. Yet they tend to be relatively short-lived and, during their lifetime, must be pruned annually. One of the most common mistakes in the care of coral trees is to give them regular water during the summer. Summer water leads to rank growth and brittle limbs, which break off during the first winter storm. The coral tree is native to South Africa, a country which, like Southern California, receives no summer rain.

Ficus Roxburghii is a curious tree with round leaves more than a foot in diameter and large figs that grow on the trunk. For years I kept my eye on a specimen growing in a yard on Victory Boulevard between Winnetka and Tampa avenues. Actually, it was more of a large shrub - around 10 feet tall - than a tree. I remember after a bad freeze one winter that all of its foliage was severely burnt or killed. However, it was robust enough to recover with renewed vigor the following spring. In the Valley, it should be planted in full sun and shielded from the wind. San Marcos Growers, a nursery in Santa Barbara, is a source for this plant. While not open to the public, San Marcos Growers supplies most Valley nurseries, and any one of them should be able to special order it for you.

Q: We live in Tujunga and have a huge oak tree. The branches and leaves look like they are dying. Our neighbors' oak trees are all green and healthy. This has just happened in the last couple of months. Is this normal?

- Carol Ohde, Tujunga

A: Before doing anything, I would make sure that your oak tree is evergreen - a so-called live oak - like your neighbors' and not a deciduous oak that loses its leaves in the winter. If you have a deciduous oak such as a Valley oak (Quercus lobata) or black oak (Quercus kelloggi), it would be normal to see leaves falling at this time. Then again, if it is an evergreen oak, the tree should be leafy year around.

Oak trees can live for hundreds of years and suddenly go into decline, usually as the result of a disease brought on by the soil-borne oak root fungus. An oak tree that has lived for years without irrigation is likely to be killed if a garden or, worse yet, a lawn is planted around it and, as a result, its roots are exposed to soil that is continuously moist.

Where a large oak tree is concerned, you should consult an arborist if you suspect that you have a serious problem. A mature oak tree adds considerable value to a property, and its removal can also be a costly affair.